Starting circuit for single-phase induction motor

a single-phase induction motor and starting circuit technology, applied in the direction of dynamo-electric converter control, dynamo-electric gear control, electric generator control, etc., can solve the problems of difficult control of the starting circuit of the single-phase induction motor, resistance is already too high for the motor to operate normally, and the triac control positive characteristic thermistor takes a relatively long time to achieve the positive characteristic of the triac control, so as to reduce the variation of the cut o

Active Publication Date: 2006-01-26
MURATA MFG CO LTD
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Benefits of technology

[0017] If the relationship of (√2×V×sin 45°) / R≧I is maintained, the motor is successfully and reliably started up.
[0018] To reduce variations in the cutoff time with the triac control positive characteristic thermistor having a volume as small as about 30 mm3,the resistance of the triac control positive characteristic thermistor must be increased and the self-generated heat must be reduced. To this end, a triac having a gate turn-on current of about 20 mA or less at an operating temperature of about 25° C. must be used.

Problems solved by technology

The starting circuit for the single-phase induction motor has difficulty in properly controlling the current so as to be cut off within a predetermined period of time (typically 1 to 10 seconds) within which the motor completes starting under varied operating temperature conditions.
Under a low temperature environment, it takes a relatively long time for the triac control positive characteristic thermistor to reach a high resistance value by self-heating.
On the other hand, under a high temperature environment, the resistance is already too high for the motor to operate normally.
With such variations, reliable operation of the motor is difficult.

Method used

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  • Starting circuit for single-phase induction motor
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  • Starting circuit for single-phase induction motor

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first preferred embodiment

[0034] The preferred embodiments of the present invention are described below with reference to the drawings. FIG. 1 is a circuit diagram of a starting circuit of a single-phase induction motor in accordance with a first preferred embodiment of the present invention.

[0035] A motor 1 includes an auxiliary coil 2 operating at the startup of the motor 1 and a main coil 3 operating to maintain the motor 1 at normal operation. In the starting circuit for the single-phase induction motor in accordance with the first preferred embodiment of the present invention, a motor starting positive characteristic thermistor 4 and a triac 7 are connected in series with the auxiliary coil 2 for starting the motor 1. A triac control positive characteristic thermistor 8 is connected in parallel with the motor starting positive characteristic thermistor 4 with one terminal of the triac control positive characteristic thermistor 8 connected to a gate terminal G of the triac 7. The triac control positive ...

second preferred embodiment

[0043]FIG. 1 is also referred to to describe a circuit diagram of a starting circuit of the single-phase induction motor in accordance with a second preferred embodiment of the present invention. The discussion of the circuit with reference to FIG. 1 is also applicable to the starting circuit for the single-phase induction motor according to the second preferred embodiment.

[0044] The starting circuit for the single-phase induction motor of the second preferred embodiment includes a triac operating at a power source voltage of about 100 V and having a triac turn-on gate current of about 30 mA at an operating temperature of about −10° C. The triac control positive characteristic thermistor 8, connected in parallel with the motor starting positive characteristic thermistor 4, includes one terminal connected to the gate G of the triac 7. The triac control positive characteristic thermistor 8 has dimensions of about 2.5 mm in diameter, about 2.5 mm in thickness, and about 12.3 mm in vol...

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Abstract

A starting circuit for a single-phase induction motor includes a motor starting positive characteristic thermistor and a triac arranged in a series connection, and a triac control positive characteristic thermistor connected in parallel with the motor starting positive characteristic thermistor, and including one terminal thereof connected to a gate of the triac. The triac control positive characteristic thermistor has a volume in the range of about 4.5 mm3 to about 30 mm3. The relationship of (√2×V×sin 45°)/R≧I is maintained with the triac control positive characteristic thermistor within an operating temperature range, where V represents a root-mean-square value of a power source voltage, R represents a resistance of the triac control positive characteristic thermistor, and I represents a gate turn-on current of the triac. The gate turn-on current I at an operating temperature of about 25° C. is about 20 mA or less.

Description

BACKGROUND OF THE INVENTION [0001] 1. Field of the Invention [0002] The present invention relates to a starting circuit of a single-phase induction motor. [0003] 2. Description of the Related Art [0004] A known starting circuit of a single-phase induction motor used in a compressor of an electric refrigerator includes a motor starting positive characteristic thermistor and a triac connected in a serial connection which is in turn connected in series with an auxiliary coil for starting the motor. A triac control positive characteristic thermistor is connected in parallel with the motor starting positive characteristic thermistor. One terminal of the triac control positive characteristic thermistor is connected to a gate terminal of the triac. [0005] In the starting circuit of the single-phase induction motor, a trigger signal, applied to the gate terminal of the triac through the triac control positive characteristic thermistor, causes the triac to be conductive. A motor starting cur...

Claims

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Application Information

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Patent Type & Authority Applications(United States)
IPC IPC(8): H02P1/42H02P21/34H02P23/00H02P23/07H02P25/04H02P27/02
CPCH02P1/42
Inventor IKEDA, YUTAKATANAKA, HIROKIHIROTA, TOSHIHARU
Owner MURATA MFG CO LTD
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